As is known, many food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material; and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH), which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating; and the web of packaging material so sterilized is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled continuously downwards with the sterilized or sterile-processed food product, and is sealed and then cut along equally spaced cross sections to form pillow packs, which are then fed to a folding unit to form the finished packages, e.g. substantially parallelepiped-shaped packages.
More specifically, the pillow packs substantially comprise a parallelepiped-shaped main portion; and opposite top and bottom end portions projecting laterally on opposite sides of the main portion and defining respective triangular end flaps to be folded onto the main portion.
A longitudinal sealing strip, formed when sealing the packaging material to form the vertical tube, extends along the pillow packs; and the end portions of each pillow pack have respective transverse sealing seams perpendicular to the relative longitudinal sealing strip and defining respective end tabs projecting from the top and bottom of the pack.
The end portions of each pillow pack taper towards the main portion from the respective end tabs, and are pressed towards each other by the folding unit to form flat opposite end walls of the pack, while at the same time folding the end flaps onto respective walls of the main portion.
Packaging machines of the above type are known which comprises;                a folding unit where pillow packs are turned into folded packages by folding means; and        a transferring and up-ending unit for tipping the folded packages.        
The folding unit substantially comprises:                a chain conveyor feeding the pillow packs along a forming path from a supply station to an output station;        a fixed elongated guide member, which is positioned facing and at a distance from the chain conveyor and cooperates cyclically with each pillow pack to flatten a first end portion of the pillow pack and so fold respective tab onto such first end portion; and        folding elements cooperating cyclically with each pillow pack to flatten a second end portion of the pillow pack and so fold respective tab onto such second end portion.        
The transferring and up-ending unit is arranged downstream from the folding unit.
The transferring and up-ending unit transfers the packages successively along a conveying path from an in-feed station to an out-feed station, and simultaneously up-ends the packages from an in-feed position, in which the packages are positioned with their axis tilted to the horizontal, into an out-feed position, in which the packages are positioned with their axis substantially vertical.
The transferring and up-ending unit receives the packages at the in-feed station from the chain conveyor of the folding unit, and feeds them to a further conveyor at the out-feed station.
More specifically, the chain conveyor supplies the unit with packages in the in-feed position, and the further conveyor withdraws the packages from the unit in the out-feed position.
The transferring and up-ending unit substantially comprises a rotary member having a number of push arms which cooperate with respective packages to remove the packages from the folding unit and push the packages along the conveying path. The transferring and up-ending unit further comprises a fixed guide extending substantially along the conveying path and cooperating with the packages to ease them from the tilted in-feed position to the out-feed position.
More specifically, the conveying path along which the packages are fed is substantially in the form of an arc of circumference, at the end of which, the packages are fed to the further conveyor.
A drawback of the known packaging machines is that it may be difficult to control the transfer of the packages from the folding unit to the transferring and up-ending unit, especially at high output rates of the packaging machines, i.e. when the packages are advanced at high speed.
If the packages carried by the chain conveyor of the folding unit are not in the right position when the push arms of the transferring and up-ending unit interact with them, the push arms are not able to remove the packages from the folding unit in the proper way. In this case, package jams may occur that lead to packaging machine stops, and so to a reduction of the packaging machine efficiency.